Why Do Crankshaft Bearings Fail? The 5 Critical Factors You Must Know

Highlights

A low oil level or a faulty oil pump can cause a lack of oil to reach the bearings.
As bearings wear, the clearance between the bearing and the crankshaft decreases, which can lead to oil starvation.
What should I do if I suspect a crankshaft bearing failure.

Crankshaft bearings play a pivotal role in the smooth operation of an engine. However, these critical components can sometimes fail, leading to catastrophic engine damage. Understanding the underlying causes of crankshaft bearing failures is essential for preventing these costly and inconvenient occurrences.

Oil Starvation

One of the primary reasons for crankshaft bearing failure is oil starvation. This occurs when the bearings are not adequately lubricated, leading to excessive friction and heat buildup. Oil starvation can result from:

Insufficient oil supply: A low oil level or a faulty oil pump can cause a lack of oil to reach the bearings.
Clogged oil passages: Dirt, debris, or metal shavings can block oil passages, restricting oil flow to the bearings.
Oil leaks: Leaky seals or gaskets can allow oil to escape from the engine, reducing the available oil supply.

Excessive Load

Crankshaft bearings are designed to withstand a certain amount of load. However, excessive load can cause the bearings to fail prematurely. This can be caused by:

Overloading the engine: Running the engine at high loads or for extended periods can put excessive stress on the bearings.
Improper crankshaft alignment: Misalignment of the crankshaft can cause uneven loading on the bearings, leading to premature failure.

Contamination

Crankshaft bearings can also fail due to contamination. Foreign particles, such as dirt, metal shavings, or coolant, can enter the oil system and cause damage to the bearings. This can result from:

Improper oil filtration: A dirty or clogged oil filter can allow contaminants to reach the bearings.
Coolant leaks: A leaking head gasket or coolant passages can allow coolant to enter the oil system, causing corrosion and bearing damage.

Bearing Wear

Over time, crankshaft bearings can wear out due to normal use. This is especially true in high-performance engines or engines that are subjected to heavy loads. Bearing wear can lead to:

Reduced oil clearance: As bearings wear, the clearance between the bearing and the crankshaft decreases, which can lead to oil starvation.
Increased vibration: Worn bearings can cause increased vibration, which can further damage the bearings and other engine components.

Manufacturing Defects

In some cases, crankshaft bearing failures can be caused by manufacturing defects. These defects can include:

Improper material: Bearings made from inferior materials may not be able to withstand the loads and stresses of engine operation.
Improper heat treatment: Improper heat treatment can weaken the bearings and make them more susceptible to failure.
Dimensional tolerances: Bearings that are not manufactured to the correct dimensions may not fit properly, leading to premature failure.

Other Causes

In addition to the primary causes listed above, other factors can also contribute to crankshaft bearing failures, such as:

Improper installation: Improper installation of bearings can cause misalignment or damage to the bearings.
Overheating: Excessive engine temperatures can weaken bearings and lead to premature failure.
Detonation: Detonation (knocking) can put extreme stress on bearings, causing them to fail.

Takeaways: Preventing Crankshaft Bearing Failures

Crankshaft bearing failures can be prevented by addressing the underlying causes. Regular oil changes and oil filter replacements can ensure adequate lubrication and prevent contamination. Avoiding overloading the engine and maintaining proper crankshaft alignment can reduce excessive load. Using high-quality bearings and having them properly installed can minimize manufacturing defects. By understanding and addressing these factors, you can extend the lifespan of your crankshaft bearings and protect your engine from costly damage.